US3550375A

US3550375A - Hydraulic ram apparatus

Info

Publication number: US3550375A
Application number: US817324A
Authority: US
Inventors: Hubert Veare Norton; Leslie Buckingham Norton; Douglas Edwin Norton
Original assignee: Norton Tool Co Ltd
Current assignee: Norton Tool Co Ltd
Priority date: 1968-04-22
Filing date: 1969-04-18
Publication date: 1970-12-29
Anticipated expiration: 1987-12-29
Also published as: GB1194623A; DE1920181A1; CH503580A; FR2006661A1

Description

Dan. v29, 1970 H. v. NORTON ETAL 31,550,375

HYDRAULIC RAM APPARATUS 4 Sheets-Sheet 1 Filed April 18, 1969 IL L nuumuriuu mm ly vm Q GE INVENTORS HUBERT v. N LE BY D0 an: 5 N32118:! MR3 s mon'rou ATTORNEY Dec. 29, 1970 H. v. NORTON ETAL 3,550,375

HYDRAULIC RAM APPARATUS Filed April 18, 1969 4 Sheets-Sheet 2 BY DOUGLA 3 E.

ATTORNEY H. v. NORTON ETAL 3 ,550,375

HYDRAULIC RAM APPARATUS Dec. 29, 1970 4 Sheets-Sheet 5 2 STTT VI RRRR CL 0000 N NNN R O e T V T N A VI B Filed April 18, 1969 Dec. 29, 1970 H. v. NORTON ETAL 3,550,375

HYDRAULIC RAM APPARATUS 4 Sheets-Sheet 4 Filed April 18, 1969 mw GI United States Patent 3,550,375 HYDRAULIC RAM APPARATUS Hubert Veare Norton, Leslie Buckingham Norton,

and Douglas Edwin Norton, Smallfield, Horley, England, assignors to Norton Tool Company Limited, Smallfield, Horley, Surrey, England Filed Apr. 18, 1969, Ser. No. 817,324 Claims priority, application Great Britain, Apr. 22, 1968, 18,826/ 68 Int. Cl. lFlSb /18 US. CI. 60-52 8 Claims ABSTRACT OF THE DISCLOSURE Hydraulic ram apparatus supplied by a single pump which delivers fluid to an actuating element for a reservoir unit whereby a large volume of fluid is delivered to the ram from the reservoir unit to produce a fast approach movement. A pressure-sensitive change-over valve switches the pump delivery from the reservoir actuator unit direct to the ram when the ram encounters resistance, to supply a smaller volume of fluid at high pressure for the working movement of the ram.

This invention relates to hydraulic ram apparatus more particularly, but not exclusively, the hydraulic ram apparatus of an hydraulic press.

In hydraulic ram apparatus it is sometimes desirable for the movable member of the ram to make a fast approach movement, which requires a large flow of fluid at low pressure, followed by a short working movement which requires a small flow of fluid at high pressure.

It is an object of the present invention to provide a means of satisfying these diverse pressure and flow rate requirements using a single pump in conjunction with a simple hydraulic system.

According to the present invention, hydraulic ram apparatus comprises a pump to supply hydraulic fluid under pressure to the working chamber of the ram through a pressure-sensitive change-over valve adapted to open only when the pressure in the working chamber attains a predetermined value higher than that during the approach movement, the pump also being in communication with the working chamber of a hydraulic cyclinder and piston unit of relatively small diameter (herein termed the reservoir actuator unit) the movable member of which is coupled to the movable member of a hydraulic cyclinder and piston unit of relatively large diameter (hereinafter termed the reservoir unit) the cylinder chamber of which communicates with the working chamber of the ram.

The change-over valve remains closed during the approach stroke, the supply of fluid in large volume and at low pressure required for the approach stroke being delivered to the working chamber of the ram from the large diameter cylinder chamber of the reservoir unit, this fluid being discharged from the reservoir unit by the advancement of the movable member thereof. The latter movement is produced by the movable member of the small diameter reservoir actuator unit which is advanced by the pump pressure acting upon it. Owing to the differences in effective diameters of the reservoir unit and of the reservoir actuator unit, only a small flow of fluid to the latter (but under medium pressure) will deliver a large flow of fluid from the former at; low pressure.

At the end of the approach movement, when the movable member of the ram encounters increased resistance, e.g. by coming up against a workpiece, the pressure in the system builds up until it attains the predetermined value at which the change-over valve is set to open. When ice this valve opens, fluid can pass directly from the pump to the working chamber of the ram, thereby applying full pump pressure to the movable member of the ram.

The cylinder space of the reservoir unit behind the piston therein may be connected by a non-return valve to a source of fluid so that fluid is admitted to this space as the movable member of the reservoir unit is being advanced during the approach movement of the ram. When the pressure in the system rises at the end of the approach movement, as mentioned above, the fluid in this space cannot escape through the non-return valve and is trapped, thereby preventing the movable member of the reservoir unit from being forced back when the change-over valve opens. Some means is necessary for venting the fluid from this space to permit return of the movable member of the reservoir unit on the return stroke of the hydraulic ram, and for this purpose the space may be connected to a line which communicates with the working chamber of the ram (e.g. a fluid return line), through a non-return valve adapted to open only when the pressure in the space exceeds the pressure in the return line (and hence in the working chamber of the ram) Thus, when a valve in the return line is opened to permit return of the movable member of the ram, the pressure in the return line will drop sufficiently to permit the last-mentioned non-return valve to open to permit fluid to escape from the said space so that the movable member of the reservoir unit is returned to its original position with the reservoir cylinder full of fluid, in readiness for the next working stroke.

It will be appreciated that in. the arrangement just referred to, in which the cylinder chamber of the reservoir unit communicates directly with the working chamber of the ram, the reservoir unit. will be exposed to the maximum working pressure of the hydraulic system and therefore must be sufliciently robust to withstand this high pressure.

In another form of the invention, the reservoir unit communicates with the working chamber of the ram through an unload valve. This valve permits fluid to flow from the reservoir unit to the working chamber of the ram during the approach movement of the ram but is automatically closed when the pressure in the working chamber begins to rise at the end of the approach movement, thereby shutting off communication between the high pressure portion of the hydraulic system and the reservoir unit. The reservoir unit therefore need not be made sufficiently strong to withstand the full working pressure and can be of relatively light and inexpensive construction.

In this form of the invention which includes an unload valve, provision has to be made for opening this valve to permit discharge of fluid from the working chamber of the ram to the reservoir unitduring the return stroke, e.g., automatically, by providing a pressure control for opening the unload valve in response to the pressure in the return chamber of the ram. The means for opening the unload valve need not, however, be pressure-actuated; it could be a mechanical connection operated by the control lever or the like which initiates the return stroke of the ram. When the unload valve is opened, fluid will be discharged from the working chamber of the ram through this open valve back into the cylinder chamber of the reservoir unit. However, since the latter part of the movement of the hydraulic ram on its working stroke had been achieved by admission of high pressure fluid through another line and not through the then closed unload valve, more fluid must be discharged to and through the reservoir unit than was originally delivered from it during the approach portion of the working stroke. For this purpose, the reservoir unit may be provided with a return by-pass passage, which permits fluid to pass back through the reservoir unit as soon as the movable member of the reservoir unit has returned to its original position.

The apparatus may have a number of refinements and modifications.

For example, there may be a bypass passage around the pressure-sensitive change-over valve, which iby-pass pasage is normally closed by a manually openable valve. When this valve is opened, direct communication is established betwen the pump and the working cylinder of the ram so that the reservoir unit and the change-over valve cease to be effective and the fast approach system is thereby rendered inoperative.

There may also be an apparatus control unit actuated against spring bias through a toggle link, for example by a pedal, which pedal is depressed to initiate a working stroke and released to initiate a return stroke.

Automatic initiation of the return stroke may be effected by providing a pressure-sensitive element adapted to collapse the toggle link when the working pressure attains a predetermined upper limit.

Various additional elements such as safety valves and overriding pressure release valves, as provided in conventional hydraulic ram apparatus, may also be installed in the present apparatus.

The invention may be performed in various ways, and two specific embodiments will now be described by way of example With reference to the accompanying drawings, in which:

FIG. 1 is a diagram showing the spatial relationship of FIGS. 1A and 1B;

FIG. 1A is the upper half of a diagram illustrating the first embodiment;

FIG. 1B is the lower half of the diagram of the first embodiment;

FIG. 2 is a diagram showing the spatial relationship of FIGS. 2A and 2B.

FIG. 2A is the upper half of a diagram illustrating the second embodiment; and

FIG. 2B is the lower half of the diagram of the second embodiment.

Referring to FIGS. 1A and 1B, there is shown in FIG. 1A the hydraulic ram of an hydraulic press. The other mechanical parts of the press are conventional and do not need to be illustrated to enable the invention to be understood.

The moveable element of the ram is a cylinder 11 which can move up and down in a fixed guide 12 secured to the frame 13 of the press. A collar 14 is attached to a screwthreaded portion 15 of the cylinder 11, and acts as an adjustable trigger for automatic repetition operation of the press in a manner to be described. Within the cylinder 11 is a piston 16 which is fixed to the frame 13. The cylinder space 17 below the piston constitutes the working chamber of the ram and is in communication with a fluid supply and return line 18 through a bore 19 in the piston 16. The cylinder space 20 above the piston 16 constitutes the return chamber of the ram and is in communication with another fluid supply and return line 21 through another piston bore 22. When fluid is supplied through the line 18 and returned through the line 21, the cylinder 11 is forced downwards to perform a working stroke, whereas when fluid is supplied through the line 21 and returned through the line 18 the cylinder is raised, performing its return stroke.

The hydraulic fluid for both the working and return strokes is supplied by a pump 25 (FIG. 1B). There is a conventional excess pressure relief valve connected to the output side of the pump, and the fluid then passes on through a main delivery line 27 to a gallery 28 in a main control valve unit 29 (FIG. 1A). In this unit there are two

valves

30 and 31 actuated by a rocking lever 32 so that when the valve 30 is open to the gallery 28 the valve 31 is closed, and vice versa. When the valve 30 is open, fluid can flow from the gallery 28 to a line 33 having two branch lines, 35 and 36 respectively. fQ f performing the working stroke of the cylinder 11 in a manner to be described in more detail below. When the valve 31 is open, the fluid can flow from the gallery 28 to the line 21 for performing the return stroke of the cylinder 11. Also, when the valve 30 is open to the gallery 28, the valve 31 vents the line 21, and when the valve 31 is open to the gallery 28, the valve 30 vents the line 33. The venting apertures beneath the

valves

30 and 31 may communicate with a fluid storage vessel (not shown). The ways in which the main control Valve unit 29 may be operated will be described in more detail below.

Between the

lines

33 and 36 there is a manually 0perable valve 37 which is closed when the reservoir unit 52 of the invention is to be operable and is opened only if it should be desired to operate the press with this unit out of action, by-passing the unit 52 and the change-over valve 41 referred to below. The line 18 communicates directly through a line 38 with the actuating cylinder 40 of the pressure-sensitive change-over valve 41. The line 35 from the line 33 leads to an inlet port 42 of this change-over valve. The outlet port 43 of the change-over valve communicates with the line 18 through

lines

44 and 38.

The line 35 also leads to the small diameter working chamber 47 of a reservoir actuator unit 48. This unit consists of a fixed tubular piston 49 the bore of which communicates with the line 35, and slidable thereon a cylinder 50. The cylinder 50 is an integral extension of the piston 51 of the reservoir unit 52, which piston is slidable in a fixed reservoir cylinder 53. The cylinder space 54 above the piston 51 constitutes a reservoir of fluid for performing a fast approach portion of the working stroke; it is in direct communication with the line 18. The space 55 in the cylinder 53 below the piston 51 can be filled with fluid from any suitable source (not shown) as the piston 51 is raised, through non-return valve 56. The space 55 also communicates with the line 35 through a non-return valve 57, such that fluid cannot flow from the line 35 into the space 55 but can blow in the reverse direction when the line 35 is vented on the return stroke.

On the return stroke, fluid can flow out of the line 18 through a return line which communicates through a non-return valve 61 with the vented line 35. The return line 60 also serves to put the line 18 in communication with a branch 62 leading to an auxiliary control valve unit 63.

The auxiliary control valve unit has an adjustable spring-loaded valve 64 which opens when the pressure in the line 18 attains a pre-set maximum value. When this occurs, fluid is admitted to a chamber 65, thereby forcing out a piston 66. The chamber 65 can be vented manually by a valve 67 actuated by a hand lever 68. Also, the chamber 65 communicates with the line 62 through a line 69 equipped with a non-return valve 70.

The rocking lever 32 which actuates the main control valve unit 29 is connected to the upper end of the upper link 72 of a

toggle linkage

72, 73. The lower link 73 of this linkage is connected to a pedal 74, and the linkage is biased towards the right in the drawing by a tension spring 75. The piston 66 engages the toggle linkage near its centre pivot. The arrangement is such that normally the toggle linkage acts as a strut, so that when the pedal 74 is depressed the toggle linkage is raised, to tilt the rocking lever 32 into the working stroke position as shown in the drawing. However, when the pressure in the return line 62 becomes high enough to open the valve 64 and push out the piston 66, this collapses the toggle linkage so that it will not transmit the pedal movement to the rocking lever 32.

The rocking lever 32 is also connected through a link 76 (FIG. 1A) to a lever 77 which is biased by a tension spring 78 so as to tend to force the link 76 downwards, to tilt the rocking lever 32 towards the return stroke position with the valve 31 exposing the line 21 to the gallery 218. Mounted in the frame 13 so as to be capable of limited upward movement is a sleeve 79 in which is adjustably mounted a pin 80. The pin 80 may be so adjusted that its lower end is engaged by the collar 14 towards the end of the return stroke, so that the sleeve 79 is thereby lifted, to raise the lever 77 and the link 76. Alternatively, the pin 80 can be raised so that it is clear of the collar 14 at all times.

The apparatus described operates as follows.

Assume that the cylinder 11 is in its upper position, ready to begin a working stroke. The pump is running and supplying fluid to the gallery 28 of the main control valve unit 29. The valve 31 is open and the pump is maintaining suflicient pressure in the return chamber 20 to maintain the ram cylinder 11 in this position. All lines and cylinder spaces are full of fluid at relatively low pressure, and the reservoir piston 51 is in its bottom position. The pin 80 is raised clear of the collar 14. If now the pedal 74 is depressed, the

toggle linkage

72, 73 will tilt the rocking lever 32 over into the position shown in the drawing so that the line 21 and the return chamber 20 are vented, and fluid is supplied through the now open valve to the

lines

33 and 35. The pressure of the fluid in the line 35 acts in the working chamber 47 of the reservoir actuator unit 48 to raise the piston 51 and force a much larger volume of fluid from the reservoir cylinder space 54 through the line 18 into the working chamber 17 of the hydraulic ram. This causes the ram cylinder 11 to make a fast approach stroke, until it encounters resistance to its further progress. At the same time, fluid enters the cylinder space 55 below the reservoir piston through the non-return valves 56. The further advance of the reservoir piston 51 is likewise resisted and pressure builds up in the line 35 and in the

lines

18 and 38. When the pressure in the line 38 has risen sufliciently to depress the piston in the cylinder of the change-over valve 41. this opens the changeover valve, thereby allowing fluid to flow from the line 35 through the

ports

42 and 43, and through the line 44 to the line 18, so that pump pressure is now applied to the hydraulic ram through line 27, gallery 28, valve 30, line 35. change-over valve 41 and line 18. This pressure is also applied to the reservoir piston 51, but this piston is now hydraulically locked by the fluid trapped in the space beneath it. This fluid cannot escape through the valve 57 because a higher pressure prevails in the line 35. The hydraulic ram therefore completes its working stroke under direct pump pressure.

When the pressing operation is complete the operator releases the pedal 74, enabling the spring 78 to swing over the rocking lever 32. This raises the valve 30, venting the line 35. This enables the non-return valves 57 and 61 to open, permitting the reservoir piston 51 to descend and the cylinder space 54 to refill, and also allowing fluid to flow out of the ram chamber 17 through the line 18 and the return line 60. At the same time, the valve 31 admits pumped fluid from the gallery 28 to the line 21, so that it enters the ram cylinder space 20 and causes the ram to perform its return stroke. The next working stroke can then be initiated by depresing the pedal 74 again.

If desired, the apparatus can be arranged to repeat its operations automatically. This is done by setting the auxiliary control valve unit 63 so that the valve 64 is opened when the pressure on the working stroke has built up to a predetermined maximum value. This causes the piston 66 to move out and collapse the toggle linkage so that the rocking lever 32 is pulled over by the spring 78 from its working stroke position to its return stroke position. Also, the pin 80 is adjusted so that it is raised by the collar 14 near the end of the return stroke, thereby raising the sleeve 79 and moving the rocking lever back from the return stroke to the working stroke position so that the cycle is repeated. During the return stroke, fluid escapes from the chamber 65 of the auxiliary control valve unit 63 through the non-return valve 70, so that the toggle linkage can re-set.

Semi-automatic operation can also be. achieved by utilizing the auxiliary control valve unit 63 but not the pin 80, or vice versa.

In the embodiment illustrated in FIG. 1A and 1B, the reservoir unit 52 is at all times in communication with the working chamber 17 of the ram and consequently exposed to the full working pressure, which may be very high. Consequently, the reservoir unit 52 must be of robust construction.

In the embodiment illustrated in FIGS. 2A and 2B the reservoir unit 82 is not exposed to pressures much above those attained during the approach movement of the ram and can therefore be of much lighter construction.

Many of the parts shown in FIGS. 2A and 2B correspond to parts shown in FIGS. 1A and 1B and have been given the same reference numerals.

So far as the pump 25, the main control valve unit 29, the pressure-sensitive change-over valve 41, the hydraulic ram 10 and the various pedal and manual and automatic control devices are concerned, these are unchanged. However, the cylinder space 54 of the reservoir unit 82 does not communicate at all times with the working chamber 17 of the ram. Instead, the cylinder space 54 communicates through a line 83, with an unload valve 84. This valve has three chambers, a chamber 85 in permanent communication with the main fluid supply line 18 to the ram working chamber, an intermediate chamber 86 with which the line 83 from the reservoir unit communicates, and an actuating chamber 87. There is a passageway 88 between the chambers 86 and 85 which can be opened and closed by a valve 89. The actuating chamber 87 communicates with the return line 21 from the ram through a line 90.

The reservoir unit 82 comprises a thin-walled cylinder 91 in which can slide a piston comprising two parts, namely an inner part 92, and an outer part 93 which is slidable axially relative to the inner part 92 through a small distance between a flange 94 and a shoulder 95 on the inner part 92. There is also an annular clearance 96 between the bore of the outer part 93 and the central portion of the inner part 92. The flange 94 is interrupted or perforated so as to permit fluid to flow down from the space 54 when the outer piston part 93 is raised clear of the shoulder 95", thereby in effect bypassing the piston. When the outer piston part 93 is in contact with the shoulder 95 such flow is prevented. A lower portion 97 of the inner part 92 serves as the cylinder of the reservoir actuator unit 48, as in the case of the previous embodiment. Fluid can pass freely into the lower cylinder space 98 below the piston 92, 93 through ports 99 in the base of the cylinder 91. Rods 100 project upwardly from the base of the cylinder.

The embodiment illustrated in FIGS. 2A and 2B works as follows.

Assume that the cylinder 11 is in its upper position, ready to begin a working stroke. The pump 25 is running and supplying fluid to the gallery 28 of the main control valve unit 29. The valve 31 is open and the pump is maintaining suflicient pressure in the return chamber 20 to maintain the ram cylinder in its upper position. All lines and cylinder spaces are full of fluid at relatively low pressure, and the reservoir piston assembly 92, 93 is in its bottom position. In this position the annular outer part 93 of the piston is resting on the rods 100 so as to lie clear of the shoulder 95 so that fluid in the reservoir cylinder space 54 can escape downwards through the piston 92, 93.

When the pedal 74 is depressed, the line 21 and the return chamber 20 are vented and fluid is supplied through the now open valve 30 to the

lines

33 and 35, as in the previous embodiment. The pressure of the fluid in the line 35 acts in the working chamber 47 of the reservoir actuator unit 48 to raise the inner piston part 92 until the shoulder 95 contacts the outer piston part 93, thereby closing the escape route for fluid from the reservoir cylinder space 54. As the piston parts 92, 93 are raised further together, they force fluid from the reservoir cylinder space 54 through the line 83 into the intermediate chamber 86 of the unload valve 84. The volume of this fluid is much greater than the volume admitted to the Working chamber 47 of the reservoir actuating unit. The pressure of the fluid discharged from the reservoir unit is sufficient to open the unload valve 84 and so permit the fluid to flow on through the line 18 into the working chamber 17 of the hydraulic ram. This causes the ram cylinder 11 to make a fast approach movement until it encounters resistance to its progress. Thereupon the pressure builds up in the line 18 and moves the piston in the cylinder 40 of the change-over valve 41 to the left (FIG. 2B) to open the change-over valve, allowing fluid to flow from the line 33 through the

ports

42 and 43 and through the line 44 direct to the line 18. This build-up of pressure in the line 18 is also suflicient to close the unload valve 84, thereby isolating the line 83 and the reservoir unit 82 from the working chamber of the ram to which high pressures are now applied.

Termination of the working stroke can be effected either by the operator releasing the pedal 74 or automatically by the auxiliary valve unit 63 as in the previous embodiment. The opening of the valve and the consequent release of pressure in the lines 33, permits the piston 92, 93 of the reservoir unit 82 to descend. At the same time, the build-up of pressure in the return line 21 and the line consequent upon the opening of the valve 31 introduces pressure into the actuating chamber 87 of the unload valve 84 so that this valve is opened once more, allowing fluid to pass back through the line 83 into the cylinder space 54 of the reservoir unit.

However, the volume of fluid discharged from the working chamber 17 is greater than the volume of the cylinder space 54, because additional fluid was introduced into the working chamber after the unload valve 84 was closed on the working stroke. Provision must be made for releasing this excess volume of fluid. This occurs when the piston 92, 93 approaches its lowest position. At this happens the outer piston part 93 comes to rest on the rods 100 but the inner piston part 92 continues to descend for a short distance, thereby opening a clearance between the outer piston part 93 and the shoulder 95 through which the excess oil can escape down through the ports 99.

On completion of the return stroke a further working stroke can be initiated either by actuation of the pedal 74 or automatically as described in the case of the first embodiment.

What we claim as our invention and desire to secure by Letter Patent is:

1. Hydraulic ram apparatus comprising a cylinder and piston unit defining a working chamber therein, a pump, a line from the pump to a pressure-sensitive change-over valve, a line from said change-over valve to said working chamber, an operative connection between said change-over valve and said working chamber adapted to open said change-over valve when the pressure in said working chamber attains a predetermined value, a reservoir unit comprising a hydraulic cylinder member and a piston member of relatively large diameter and defining a reservoir chamber therein, one of said members being movable, a line from said reservoir chamber to said working chamber, a reservoir actuating unit comprising a cylinder member and a piston member of relatively small diameter one of which members is movable together with said movable member of said reservoir unit, and a line from said pump to said reservoir actuating unit.

2. Apparatus according to claim 1 in which said members of said reservoir unit define a cylinder space separated from said reservoir chamber by said piston member, and including a non-return valve for fluid openable inwards towards said cylinder space.

3. Apparatus according to claim 2 including a nonreturn valve for fluid openable outwards from said cylinder space to a line communicating with said working chamber.

4. Apparatus according to claim 1 in which there is an unload valve in said line from said reservoir chamber to said working chamber to permit flow of fluid from said reservoir chamber to said working chamber only when the pressure in said working chamber is below a predetermined value.

5. Apparatus according to claim 4 including means to automatically open said unload valve to permit return flow of fluid from said working chamber to said reservoir chamber during a return stroke of said ram, said means being responsive to pressure in a return chamber of said ram.

6. Apparatus according to claim 4 including means defining a return by-pass passage in said reservoir unit to permit flow of fluid from said cylinder space when said movable member of said reservoir unit has returned to its original position.

7. Apparatus according to claim 1 including a bypass line around said pressure-sensitive change-over valve and a normally closed valve in said by-pass line.

8. Apparatus according to claim 1 including a control unit, spring means urging said control unit in one direction, a toggle linkage, a control member adapted to urge said control unit in the opposite direction through said toggle linkage, a pressure-sensitive element, means of connecting said pressure-sensitive element to said working chamber, and an operative connection between said pressure-sensitive element and said toggle linkage to collapse said toggle linkage when the pressure in said working chamber attains a predetermined upper limit.

References Cited UNITED STATES PATENTS 2,403,391 7/1946 Muir 60--52H.F. 2,827,766 3/1958 Hufford 6052H.F.X 3,310,943 3/1967 Horetzke 60--52H.F.X

FOREIGN PATENTS 797,753 7/1958 Great Britain 60-52H.F.

EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R. 91-2